1. Field of the Invention
The present invention relates to boring heads for rotary tools, and, in particular, to boring heads with imbalance compensation.
2. Description of the Related Art
Boring heads are used primarily for machining close tolerance bores. Since, due to their construction, they are not rotationally symmetrical, they will be imbalanced to a greater or lesser degree. This imbalance has a negative effect on the vibrational behavior of the tool and therefore on the boring process. Such imbalance reduces the dimensional and shape precision as well as the surface quality of the bores. The development of increasingly hard and more heat-resistant cutting materials and the demand for shorter machining processes have resulted in increasingly higher rotation speeds and with it an increased need to avoid imbalance.
German patent application DE-C-35 10 259 discloses a boring head, in which imbalance compensation is provided by two weights that are installed on the circumference of the tool head, connected to a cable line, and movable in opposite directions by means of a graduated ring. The weights have the shape of semicircular disks that are capable of pivoting in opposite directions about a common pivot point by means of pull lines affixed to them leading to direction-changing bolts. This imbalance compensation device occupies a relatively large space vertically and is expensive to install and maintain. In addition, U.S. Pat. Nos. 5,074,723 and 5,263,995 teach boring heads that have, for imbalance compensation, two weights designed as rings that move independently of one another. Here, too, the arrangement of the rings one above the other requires a relatively large space.
Finally, German patent application DE-C-42 42 063 discloses a boring tool in which a weight is automatically moved by a lever arm independently of the diametral movement. In a boring head intended to be used with bit supports of different weight, automatic imbalance compensation is unsuitable.
An objective of the present invention is to provide a boring head that makes imbalance compensation possible in a relatively simple manner and that can be produced economically. Further aspects and advantages of this invention will become apparent from the detailed description which follows.